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Anatomy for neurotrauma
Published in Hemanshu Prabhakar, Charu Mahajan, Indu Kapoor, Essentials of Anesthesia for Neurotrauma, 2018
Vasudha Singhal, Sarabpreet Singh
Internally, the pons is divided into a ventral, basilar part and a dorsal, tegmental part. The basilar part is a continuation of the pyramids, which contains longitudinal fibers of the corticopontine, corticonuclear and corticospinal tracts descending from the crus cerebri of the midbrain. The dorsal tegmentum of the pons contains the motor nuclei of CN V, VI, VII, and VIII. The medial and lateral lemniscus and the pontine part of the reticular formation also lie in the tegmentum.
Discussions (D)
Published in Terence R. Anthoney, Neuroanatomy and the Neurologic Exam, 2017
For some reason, as the various tracts within “the lemniscus” were identified, the only ones named as separate lemnisci (e.g., medial lemniscus, lateral lemniscus, spinal lemniscus, trigeminal lemniscus) were ascending tracts that terminated most rostrally in the thalamus. Descending tracts and other ascending tracts were not named as lemnisci. Consequently, the term “lemniscus”came to be associated with tracts conveying sensory information to the thalamus, which tend to be made up of crossed (= decussated) secondary fibers (see the discussion of Semantic Contlicts 3–4 under D: Lemniscus for exceptions, however). If One foCUSes On these associations, it is easy to see why some authors would not include the spinotectal tract as part of the spinal lemniscus, for the spinotectal tract does not ascend to the thalamus. On the other hand, if one focuses on the common origins and intermingling of the fibers in the tracts, it is easy to see why some other authors would consider the spinotectal tract to run in the spinal lemniscus. In that case, however, it is somewhat surprising that no recent authors have been noted to include the spinoreticular tract(s) in the spinal lemniscus. Perhaps it is because many recent authors do not yet describe separate spinoreticular tracts (see the discussion of Semantic Conflict 4 under D: Spinothalamic tract for details).
Psychobiological foundations of early sensory-motor development and implications for neonatal care
Published in Philip N. Murphy, The Routledge International Handbook of Psychobiology, 2018
Victoria Dumont, Maryse Delaunay-El Allam, Nadège Roche-Labarbe
The somatosensory system underlies the perception of a wide range of stimuli. It can be subdivided into four functionally distinct subsystems: tactile perception, proprioception, nociception and thermoception. Each has a specific set of peripheral receptors — in the skin, muscles and joints — and neural pathways (for a complete review, see Abraira & Ginty, 2013). The receptors can be distinguished according to the type of stimulus to which they respond, and according to their anatomical situation (exteroceptors or interoceptors). The tactile subsystem is sensitive to the size, shape and texture of objects and their movement on the skin. Four types of tactile cutaneous receptors, distributed throughout the body, were identified. The Merkel discs and the Meissner corpuscules are receptors involved in discriminative touch. They have small and well-defined cutaneous receptive fields and are located in the superficial layers of the skin (dermal–epidermal junction). The Ruffini receptors and the Pacini corpuscules, located in the deeper layers of the skin (dermis) and the subcutaneous tissue, have wide and blurry receptive fields and are involved in non-discriminative touch. Proprioception refers to the perception of one’s body position and movements, and depends on mechanoreceptors in muscles and joints. Neuromuscular spindles are sensitive to muscle length, articular receptors are sensitive to the position of the joints, and Golgi tendon organs are sensitive to muscle tension. Both tactile and proprioceptive information is conveyed to the brain via the lemniscus pathway. Nociception refers to pain perception, and thermoception to the perception of temperature. Both are supported by highly arborized free nerve endings, transmitting information to the brain by slow unmyelinated (C) and fast myelinated (Aδ) fibres through the spinothalamic pathway.
Bilateral Tapia’s syndrome secondary to cervical spine injury: a case report and literature review
Published in British Journal of Neurosurgery, 2023
Alexandros G. Brotis, Jiannis Hajiioannou, Christos Tzerefos, Christos Korais, Efthymios Dardiotis, Kostas N. Fountas, Kostantinos Paterakis
TS involves dysfunction of the X and XII cranial nerves (CN); Thus, it should be differentiated from a number of syndromes that involve multiple lower CN and present with vocal cord paralysis, dysarthria, and tongue deviation (Table 1). As a matter of fact, the paucity of symptoms and signs from the trunk and extremities excludes a number of eponymous medullary lesions involving the pyramidal tract and/or the medial lemniscus (Avellis, Jackson, Schmidt, Wallenberg, and Dejerine-Bousy syndromes). Preservation of the sternocleidomastoid and trapezius muscles function provides further evidence to rule out pathologies involving the XI CN (Collet-Siccard, Jackson, MacKenzie, Vernet, and Villaret syndromes). Finally, the sign of tongue paresis ruled out syndromes preserving the 12th CN (Avellis, Eagle, Schmidt, and Vernet syndromes).
CI in single-sided deafness
Published in Acta Oto-Laryngologica, 2021
Anandhan Dhanasingh, Ingeborg Hochmair
The auditory pathway starts in the cochlea from the inner hair cells of the organ of Corti which send the signal to the spiral ganglion cell bodies (SGCB) through the peripheral neural fibres in response to the acoustic signal. The central axons of the SGCB form the cochlear nerve, and the vestibular nerve joins the cochlear nerve entering the internal auditory meatus (IAM) – commonly called as cochlear-vestibular nerve – which is a clinically relevant location, as any damage to it would normally affect both, auditory and vestibular functions. The nerve in the IAM travels a short distance of around 1cm to reach the surface of the brainstem at the ventral (anterior) cochlear nuclei (CN). Until CN, the neural fibres coming from each ear are kept separated on their own sides. The neural fibres from the ventral CN extend to the dorsal (posterior) CN, and from here most of the fibres cross the midline, travelling up in the contralateral (opposite) lateral lemniscus. At the same time, some fibres travel up in the ipsilateral (same side) lateral lemniscus. From the ventral CN, most of the neural fibres travel up to reach the contralateral superior olivary nuclei, whereas some neural fibres reach the ipsilateral superior olivary nuclei as well (Figure 1).
Intraoperative Neuromonitoring and Lumbar Spinal Instrumentation: Indications and Utility
Published in The Neurodiagnostic Journal, 2021
Ryan C. Hofler, Richard G. Fessler
Most IONM modalities fall into one of three main categories. Somatosensory-evoked potentials (SSEPs) are recorded cortically and subcortically in response to continuous stimulation of select peripheral nerves, such as the tibial and peroneal nerves during lumbar spine surgery, thereby assessing the somatosensory pathways of the posterior column-medial lemniscus. Motor-evoked potentials (MEPs) reflect function of the corticospinal tract elicited by applying intermittent electrical transcranial stimulation with recordings made in the form of compound muscle action potentials from various bilateral upper and lower extremity muscle groups. Electromyography (EMG) can be performed continuously (c-EMG) to assess the function of an individual myotome throughout a procedure or can be triggered (t-EMG) at specific points in a procedure for the purpose of nerve detection and compromise (Biscevic et al. 2020; Fehlings et al. 2010; Lall et al. 2012). In the present discussion, we present several approaches to the instrumentation of the lumbar spine with accompanying uses for multimodal IONM to maximize complication avoidance.